Storyline: Sophomore Jay Ajayi, who averaged 6.7 yards per carry as a backup last season, takes over the featured role in the backfield. Despite his youth, he is the longest-tenured tailback on the team and has been pushed into a leadership role. “He did a great job in the offseason really leading the group,” running backs coach Keith Bhonapha said. “The drills that we needed during the summertime for these guys to progress as a group, he kind of supervised those. As we’ve gotten out here in fall camp, he’s been the guy really trying to keep the younger guys motivated when he’s not practicing and when he’s in, he’s really trying to go out there and lead by example.”

Keys to success: The Broncos will need the young group to step up in three areas that can be troublesome for inexperienced backs — ball security, pass protection and goal-line running. There’s no doubt the group has enough talent to produce big yardage. “I really think that every guy in that backfield, if they’re playing at their very best and can stay healthy, every guy has a chance to be the guy,” coach Chris Petersen said.

Reason for concern: Ajayi is the only tailback who was on the team before August of 2012. If anything happens to him, the Broncos will have as inexperienced of a backfield as any team in the country.

Star player: Ajayi is primed for a breakout year in a backfield that has produced four straight 1,000-yard rushers — a feat accomplished by three different players. “He’s a very humble individual,” Fields said. “He just works hard every day. He helps all the younger guys out with pass protection and things like that.”

Breakout performer: Thomas, the transfer from Butler Community College, is a talented runner who’s used to competing for playing time in a crowded backfield. “Any time you get a junior college guy, they know their time is limited,” Bhonapha said, “and he knows that on that field is where he wants to be. So he takes that focus and the preparation and is going hard 24/7.”

Newcomer to watch: Thomas, of course. But Baltazar could be interesting. He probably is one of the top four tailbacks but if he doesn’t crack the top three, it might not be worth burning his redshirt season. The Broncos have leaned toward using true freshmen, even in a limited role, in recent years. “Aaron is a really smart kid,” Bhonapha said. “He understands the offense for the most part. He’s a true freshman, so he has those mistakes pop up every once in a while, but you talk about a guy who has great savvy out there on the football field. It’s not too big for him so far at practice. I’m really excited to see what the future holds for him.”

— The Broncos’ tailbacks averaged 5-foot-10, 190 pounds in 2008. Martin was the heaviest at 200 pounds. This year, they average 5-10, 201. Four players weigh at least 200 pounds — and two of them are freshmen.

— Bhonapha on Fields, who played as a true freshman: “Jack has made a lot of progress since last year. I will tell you this: Him going through the offseason program and the spring and now the summertime has helped him. He’s gotten faster. You can tell he has a little more savvy to him.”

— Petersen on the big backs: “We definitely like big guys at all positions but we’re always into good football players. We’ll take a smaller guy at whatever position if we think he’s good. It’s nice when they’re big and good. They’re harder to tackle — we know that for sure.”

— Petersen on Fields: “He’s one of those guys you’re always rooting for because he is such a great kid. A really good student. He comes from a great family. And he’s tough and a hard worker. Those are the guys you really like to coach.”

— Ajayi: “I definitely think losing weight will add an extra gear in my game and will be better for my knee.”

— Ajayi on the group: “We’re deep. We’re all very talented. We all bring a different style of play to the running back position. I’m excited for all of us to get out there and show what we can do.”

— Thomas: “I get more comfortable every day. The more comfortable you are, the better you play. … Whatever you need me to do, I can do. If I need to get to the end zone, you’ll be surprised how I get there.”

— Thomas on the group: “It’s just a good feeling to be with this group because we’re all starving, we’re hungry. We’re going to do whatever it takes to get where we want to be.”

Running back spin moves

Jay Ajayi interview

•••

Boise State junior defensive end Demarcus Lawrence has been a force throughout fall camp and Petersen recognized him Friday as his camper of the day.

Lawrence, who didn’t play in the bowl game last year because of his second team-rules suspension, has shown the consistency that was missing last year.

“Demarcus has had great energy out here,” Petersen told BroncoSports.com. “He’s running to the ball and he has had a relentlessness about him all camp — exactly the way we want our defensive linemen to play.”

Lawrence led the Mountain West with 9.5 sacks last season. He also was fifth on the team with 48 tackles and first with 13.5 tackles for loss.

The second-team offense got a big play from junior wide receiver Dallas Burroughs, who made a leaping catch in tight coverage along the sideline and ran for another 25 yards or so. It was a terrific throw from backup quarterback Grant Hedrick. But that drive ended on a botched snap.